The existence of antigen specific helper and suppressor factors has been documented in vitro. Since these substances have therapeutic potential in regulating undesirable Immune responses it is essential to evaluate their role in vivo in mice. Previous work has involved model antigens (proteins or synthetic polypeptides) but now we wish to employ antigens of biological importance, and have chosen Insulin because it is well defined and studied, and anti Insulin antibody is a common problem in diabetes. Thus we will develop in vitro and in vivo assays for helper and suppresor cells (and their factors) reactive to Insulin. Attempts will be made to induce human suppressor cells in vitro, and to analyze their function, and characterize the products biochemically. Subsequently human helper and suppressor cells to Insulin will be generated and assayed, initially in mouse systems, but eventually in human antibody response systems in vitro. As large quantities of helper or suppressor factor would be required if ever these were to be used for specific immunotherapy, it is planned to produce hybrid cell lines releasing such factors. Some of these have been produced in a totally mouse system, but attempts will be made to generate lines producing human helper and suppressor factor to important antigens such as Insulin. Such factors will be tested both in vitro and in vivo.